Field of the Disclosure
The present disclosure generally relates to telecommunications, and more particularly, to a voltage regulator for generating supply voltages to support a subscriber line.
Description of the Related Art
In communications systems, particularly telephony, it is common practice to transmit signals between a subscriber station and a central switching office via a two-wire bi-directional communication channel. A line card generally connects the subscriber station to the central switching office. A line card typically includes at least one subscriber line interface circuit (SLIC) as well as a subscriber line audio-processing circuit (SLAC). The functions of the line card range from supplying talk battery to performing wake-up sequences of circuits to allow communications to take place.
Subscriber line interface circuits (SLICs) have been developed to provide an interface between a low voltage signal path in a telephone central office and a high-voltage telephone subscriber line. The SLIC provides functions such as off hook detection, ringing signal generation, and battery feed to the subscriber line. The subscriber line consists of a telephone transmission line, including two conductors referred to as A and B or tip and ring, and the subscriber telephone equipment coupled across the tip and ring conductors (i.e., the load). A SLIC provides power from the telephone central office to the subscriber line in response to a received battery voltage. DC battery voltages are provided to the SLIC to power the SLIC and the subscriber line. For example, a low negative voltage source, VBL, and a high negative voltage source, VBH, are typically provided to the SLIC. The VBL source is generally used during off-hook operation to support a call. The VBH source is generally used during on-hook operation and to support ringing.
Conventional techniques for generating the SLIC input voltages include per channel power supplies (separate power supplies for voltage source) or shared, multiple output power supplies. While per-channel battery voltage generation can be implemented with a relatively low-cost inductor, it requires one inductor per channel, which contributes to the total cost and real estate consumed by the power supplies. A shared multiple output approach requires a single higher-cost transformer with multiple output taps to allow the different output voltages to be generated.
The use of the same reference symbols in different drawings indicates similar or identical items.